1. Field of the Invention
The present invention relates to improvements of the power brush of a vacuum cleaner which is provided with the power brush.
2. Prior Art
Accessories for home cleaners include a nozzle with a round brush and a narrow air suction opening for use in narrow places, and a floor brush exclusively used for floor cleaning with a wide air suction opening at the bottom. In recent years, as the use of carpets has been common in ordinary houses, more and more home vacuum cleaners have come to be equipped with power brushes to clean carpeted floors. A power brush in which a floor brush is driven by a built-in motor is well known. As is known, a panel floor forms a relatively flat, hard floor surface while a carpeted floor that is made of fibers has a floor surface having portions resiliently recessed and raised, forming a relatively soft floor surface.
FIG. 14 shows a top cross-sectional view of a prior art power brush and FIG. 15 illustrates a side view of the prior art power brush when it is placed on a floor 7.
At the bottom of a casing 1 facing the floor surface is provided an air suction opening 2 through which brush members 3a of a rotary brush 3 project slightly toward the floor surface. The rotary brush 3 has ridges and furrows extending in a spiral form in axial direction thereof and brush member 3a are implanted into the ridges along their lengths. The rotary brush 3 is driven by a motor 4 via a belt 5 which in turn is driven and controlled by a control circuit 6. Wheels 9 carry the main body of the power brush built in the casing 1 and serves to maintain the casing 1 at a predetermined height on the floor surface as well as to form a flow path for sucked air into the opening 2. Dust and air sucked through the opening 2 are directed to a hose-mounting portion 8, slightly tapered at its tip end, and are delivered into the cleaner body through a flexible hose, not shown, to be connected to the hose-mounting portion 8. The electric power for the power brush is supplied through a connector 10.
In the case where the carpeted floor is cleaned by the power brush, the motor is operated to drive the rotary brush 3 into rotation so that dust between fuzzy hairs or texture of the carpet is brushed out by the brush member 3a and is sucked together with air into the hose. Thus cleaning is effected. In the case where the hard flat floor is to be cleaned, the rotary brush 3 is not driven but air is merely sucked.
A person using this type of power brush, therefore, has to watch the floor at all times to manually turn on the motor when the cleaner moves onto the carpeted floor, and to turn it off when it is on the panel floor. This manual switching is a nuisance for the operator. Because of this, the operator may wish to lift the cleaner to carry around from one place to another, across a hard, flat floor while the motor is running. The idle operation of the motor, however, is not only dangerous but also a waste of electric power. In Japanese houses where the hard, panel floor and the carpeted floor coexist, it is a serious problem to frequently switch on and off the power brush motor. Improvement has been long waited.
FIG. 16 illustrates another prior art vacuum cleaner disclosed in Japanese Utility Model Publication No. 58-17588 and FIG. 17 shows a floor detector used for the cleaner. In FIGS. 16 and 17, when a power switch is turned on, a motor within a body 61 runs to drive a rotating cleaning member, not shown, in contact with a floor surface 11, thereby effecting cleaning. When the body 1 is lifted, a shaft 65 displaces relative to an elongated hole 66 due to the weight of the wheel 64. As a result, an actuator 63 is allowed to further project, causing a safety switch 60 to become opened. In this manner, lifting the body 61 automatically causes rotation of the cleaning member to stop, thus eliminating the potential of contact accidents between the rotating cleaning member and the operator's body.
This type of apparatus, however, suffers from drawbacks in that dirt and dust from the floor easily adheres to the actuator of the safety switch, disturbing the smooth open and close operation of the switch. Moreover a mechanical contact of the switch can be a source of chattering of the switch due to the bounce of the contacts.
The fact that the actuator is operated by the weight of the wheel 64 causes another shortcoming. That is, when the body is lifted and turned its bottom side up for inspection, etc., the shaft 65 slides toward top side of the body in the elongated hole. The shaft 65 again pushes the actuator to activate it, causing the rotating cleaning member to suddenly rotate. Thus rotating cleaning member may injure operator's fingers or hands.